1. Field of the Invention
The present invention pertains to a high power, pulsed microwave frequency converter for use in a microwave communications system and/or radar systems. The high power converter is generally utilized in a transmitter for a communications system with a local oscillator and an intermediate frequency reference source controlling the output frequency. Typical microwave communications systems in which the present high power, pulsed microwave frequency converter finds application are missile guidance radar, offset frequency coherent transponders, ECM systems, coherent radar test sets, etc. wherein the systems require coherent pulsed transmitters.
2. Brief Description of the Prior Art
The conventional coherent solid state transmitter includes a series of oscillators injection locked from a reference signal that is on the order of one milliwatt. The typical gain per stage is 13 dB. For a transmitter with 10 watts of power this may mean as many as four injection locked oscillators in series. With this many oscillators in the circuit, problems such as temperature drift, power efficiency and reliability are greatly increased. Frequency conversion is obtained by using a low level single side band modulator to drive the series of injection locked oscillators.
There has been some work published on pulsed AFC loops where the time to lock is important, but these are not coherent systems. Further some prior art involved CW applications where the lockup time is of little or no significance. One such application may be found in U.S. Pat. No. 3,895,312, entitled "Low Noise High Spectral Purity Microwave Frequency Synthesizer", issued July 15, 1975. This patent relates to a microwave frequency synthesizer which uses a phase locked loop to perform a signal frequency conversion. This is not a pulse system and there is no teaching of operating this system with a narrow pulse. Further, there is no requirement or teaching that this system could replace the prior art injection locked series of oscillators to provide the high power required.